[Dynamite] ANSI C question

[Ewan Birney]

On Wed, 22 Mar 2000, Ian Holmes wrote:

> GLib uses casts to implement "private" data, e.g.
> 
> struct _GArray
> {
>   gchar *data;
>   guint len;
> };
> 
> in "glib.h", which is then casted to
> 
> struct _GRealArray
> {
>   guint8 *data;
>   guint   len;
>   guint   alloc;
>   guint   elt_size;
>   guint   zero_terminated : 1;
>   guint   clear : 1;
> };
> 
> Do either of you know if this is strict ANSI, i.e. can we be sure that the
> first two fields of _GArray (data & len) are mapped to the same memory
> locations as data and len in _GRealArray in all C compilers?

This is strict ANSI interestingly. (read the back of K&R about struct
layout).

> 
> If so it makes life a lot easier...


This trick is what GTK uses for inheritance.


> 
> Ian
> 
> -- 
> Ian Holmes  ....  Howard Hughes Medical Institute  ....  ihh@fruitfly.org
> 
> 
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